Did you have a good windscreen? That usually improves efficiency considerably, as does some sort of a lid on the container. I don't think I have ever seen a lid for a GI canteen cup, but one can be easily made from aluminum flashing or even heavy duty foil....
I know of at least TWO lids for a GI canteen cup.
A plastic lid:
http://www.bestglide.com/canteen_cup_lid.htmlA stainless steel lid :
http://www.thekeytosurvival.com/storetitles/stovescookware/heavyboilcover.htmlNeither lid is USGI.
It would appear neither lid will fit in a USGI canteen cover along with the canteen, canteen cup and stove. I am sticking with aluminum flashing for this exact reason.
Thanks.
Conway Yee